While riding an entity with an offset position, there is a mismatch between the player's position as shown in F3 and the the results of /data get entity @s Pos

reproducing:

1. Place a chest boat down

2. Enter the chest boat

3. Open the F3 screen

4. Run /data get entity @s Pos

Expected result:
The values of coordinates should match with values acquired using /data command

Actual result:
/data get command displays values as if there was no offset

also applies to:
boat(with 2 passangers)
camel
happy ghast